In late years, a fabricating method of a MOSFET (Metal Oxide Semiconductor Field Effect Transistor) using a film made of a high dielectric constant material as a gate dielectric film is suggested. According to the method, the physical film thickness of the gate dielectric film is increased to suppress generation of gate leakage current and the electric film thickness of the gate dielectric film is decreased. For example, Hf compound such as HfO2 or Zr compound such as ZrO2 is used for the high dielectric constant material.
In addition, a technique to cap upper surface of high dielectric constant gate dielectric film made of HfO2 with a La2O3 film to decrease threshold voltage of an N-type MOSFET is known. The technique, for example, is disclosed in a non-patent literary document of V. Narayanan et al., 2006 Symposium On VLSI Technology Digest of Technical Papers, pp. 224-5.
Furthermore, a technique to cap upper surface of high dielectric constant gate dielectric film made of HfSiON with an Al2O3 film to decrease threshold voltage of a P-type MOSFET is known. The technique, for example, is disclosed in a non-patent literary document of K. Sekine et al., Extended Abstract (The 67th Autumn Meeting, 2006); The Japan Society of Applied Physics, p. 716.
Moreover, it is known that existence of La between an interface dielectric layer made of SiO2 or SiON, which is formed on a channel region, and a high dielectric constant gate dielectric film made of Hf compound such as HfO2 or HfSiON is needed. This, for example, is disclosed in a non-patent literary document of Y. Yamamoto et al., Extended Abstracts of the 2006 International Conference on Solid State Devices and Materials, pp. 212-3.